Seat track assemblies are commonly used for forward and rearward comfort adjustment of seat assemblies, particularly seat assemblies affixed in motor vehicles. Such seat assemblies normally have a seat base and a seat back, with the seat back pivotably connected to the seat base by a recliner. The seat base is commonly mounted over a pair of upper seat tracks which are slidable over a pair of lower seat tracks. Each upper track is releasably secured to its corresponding lower track by a latch mechanism operable by a release lever, "towel bar" or other well known device. Such seat track assemblies used in motor vehicles are typically attached to a floor pan and optionally to side pillars so that each lower track and other componentry rigidly attached to each lower track are fixed with respect to the motor vehicle, and the upper tracks and the componentry mounted to them (that is, the seat cushion, etc.,) are adjustable to a range of fore-and-aft positions.
The upper and lower tracks are vertically interlocked, often with a reduced friction interface between them for ease of fore-and-aft position adjustment, such that the seat cannot be easily vertically dislocated from the lower tracks. Greater vertical dislocation forces may be experienced, however, than the interlocking tracks can withstand without unacceptable levels of permanent deformation or other damage. This is especially true for seat assemblies in which a seat belt system is mounted directly to the seat assembly, known as "all-belts-to-seat" designs, rather than to the side pillars or to the floor pan. U.S. Pat. No. 5,362,132, issued to Griswold et al, and U.S. Pat. No. 5,322,348 issued to Johnson illustrate the known approach of employing exterior mounted J-hooks to anchor a seat cushion frame to the lower track sub-assembly against upward dislocation forces. In the normal operation, upper and lower J-hooks are free to slide past one another during comfort adjustment of the upper track with respect to the lower tracks. In the event of high vertical dislocation forces, however, the seat cushion frame would lift only until the upper J-hook contacts its fixed counterpart. Thus, the J-hook arrangement enables the vehicle seat to withstand vertical dislocation forces beyond the level which can be withstood by the more lightly designed interlocking seat tracks.
While such known J-hook arrangements are useful in withstanding excessive vertical dislocation forces, they tend to be relatively expensive and bulky. This is particularly undesirable in seat track assemblies used in motor vehicles where interior space is at a premium and there is continuous pressure to reduce costs.
In view of the foregoing, it is an object of the present invention to provide a seat track assembly with enhanced resistance to vertical dislocation forces which is of low cost and reduced size. Additional objects and features of the invention will become apparent from the following disclosure and detailed description of various preferred embodiments.